Method of forming threaded caps for containers



April 28, 1931. w KOWAL 1,803,022

METHOD OF FORMING THREADED CAPS FOR CONTAINERS Filed NOV. 22, 1929gwuentoo WALTL'R K Patented Apr. 28, 1931 UNITED I STATES PATENT OFFICEWALTER KOWAL, OF NEW YORK, N. Y., ASSIGNOR. TO BHOENIX-HERMETIC COMPANY,OF BROOKLYN, NEW YORK, A CORPORATION OF NEW YORK METHOD OF FORMINGTHREADED CAPS FOR CONTAINERS Application filed November 22, 1929. SerialNo. 409,049.

The invention relates to new and useful improvements in a. method ofmaking screw caps for containers, and more particularly to a screw capwhich is made from metal having thesurface thereof decorated.

An object of the invention is to provide a method of forming the threador threads in the screw cap whereby said threads may be made of thedesired depth to properly engage the holding threads on the neck of thecontainer without injuring or marring the decorated surface of the capor rupturing the metal of the cap itself.

The invention consists in the forming of a hat-shaped blank from a sheetof metal by drawing, then by the aid of rolling dies forming a shallowthread depression in the vertical wall of said blank, and finallysubjecting the blank to pressure in a direction endwise of the verticalwall for bending the metal in said thread depression to complete theformation of the thread. The lower edge of the blank is preferablycurled.

In the drawings Figure l is a View partly in side elevation and partlyin section showing a hat-shaped blank from which the screw cap isproduced.

Fig. 2 is a similar view showing the blank after it has been subjectedto the rolling dies for forming a shallow thread depression in thevertical wall thereof, and also after the lower edge of the blank hasbeen curled.

Fig. 3 is a similar view of a completed cap.

Fig. 4 is a view showing the means for supporting the blank and forpressing the same with the blank in place and prior to the applying ofpressure thereto.

Fig. 5 is a similar view, butshowing the pressure applied and the threadcompleted.

Fig. 6 is an enlarged sectional view through aportion of a finished capand a portion of a bottle neck showing the cap appplied to the bottleneck.

It is a common expedient to form screw caps from metal for bottles byfirst forming a hat-shaped blank and then subjecting said blank to theaction of rolling dies for curling the edge and rolling a thread in thevertical side wall of the blank. In order to make these threads ofsufiicient depth to co operate with the holding threads on the neck ofthe bottle, in caps the bending of the metal is so excessive that therolling dies often break the decorated surface -of the metal andsometimes rupture the metal itself. Furthermore, in a very small cap itis difiicult to properly form the threads of proposeddepth solely by theaid of-rolling dies.

The invention is directed to a method of forming a screw-thread metalcap whereinthis excessive pressure of the rolling dies is avoided. Tothis end the metal is first drawn to form a hat-shaped blank in theusual manner, and this hat-shaped blank is subjected to a rolling diepressure for forming a very shallow thread depression in the verticalwall of the blank. The flange is also curled by the aid of rolling dies.This initial formation of the thread depression which is very shallowdoes not shorten to any material extent the length of the vertical wall,and the pressure necessary to form a shallow thread in the vertical walleven when the cap is very small is not so excessive tical wall of theblank isof greater length than the vertical wall desired in the finishedcap. The cap thus formed is placed on an anvil or supporting horn: whichextends into the cap. This supporting horn is of a diameter equal to theinternal diameter of the thread in the completed cap. The height of thehorn or anvil is likewise the height of the wall of the finished cap andis, therefore, considerably less in height than the wall of the blankwith the shallow thread depression therein. The cap thus formed isplaced on this anvil and thenpressure is applied thereto for shorteningthe vertical wall and for bringing the pitch of the thread to the normaldesired pitch to cooperate with the neck in Fig. 1 the hat-shaped blankis indicated at 1. Said hat-shaped blank includes a vertical wall 2, atop portion 3 and a flange 4. This hat-shaped blank is formed from asheet of metal by drawing and cutting in the usual manner. The blank issubjected to rolling dies for forming a knurl at the upper end of thecap, curling the lower edge, and for providing a shallow threaddepression in the vertical13all 2 of the blank. The curling, knurling,and threading may all be formed in a single operation, or they may beformed in separate operations. The knurl is indicated at 5 in thedrawing, the curl at 6, and the shallow thread depressions at 7.

It will be noted that the vertical wall 2 of the shallow threaded blankis substantially the same length as the vertical wall 2 of thehat-shaped blank. The formed thread is so shallow that the wall is notshortened to any great extent, but the depressions determine the finalthread and crease the metal to such an extent that an endwise pressureon the vertical wall will complete the forming of the thread. The pitchof the thread after the shallow threading operation is indicated by theline ww in Fig. 2 and this pitch is greater than the pitch of theholding thread on the neck of the bottle with which the cap is to beused. The knurled, curled and threaded blank as shown in Fig. 2 isplaced on an anvil or horn 8 carried by a suitable supporting means 9.The diameter of this horn is indicated by the line r, and is slightlyless than the inner diameter of the threaded blank as shown in Figs.

2 and 4. The height of the horn indicated by the line 8 is less than theheight of the vertical wall 2 of the shallow. threaded blank. After thecap has been placed on this horn or anvil a pressure member 10 islowered into contact with the top 3 of the blank and pressure isapplied, moving this member 10 to the position shown in Fig. 5. Thispressure member has a recess 10 in its under face, which receives thetop portion of the cap, and this centers the cap relative to the horn oranvil 8. There is a laterally projecting flange 11 associated with thehorn and said flange is provided with a raised portion 11 forming arecess 11 which receives the lower curled edge of the blank. Inasmuch asthe lower curled edge is restin on the flange and is limited in itsoutwar other, it will be limited by this horn in its inward movement andthe remaining portion of the thread will likewise be forced inward to asimilar extent. this horn 8 is made of true circular form and the threadbeing forced into engagement all the way around will produce a capwhichis true and round as well as a thread which is of proper size.

It will, be noted that the depression in the vertical wall of the blankis more acute at the bottom of the depression as viewed from the outerface of the cap. Therefore, the endwise pressure on the vertical wallwill cause the metal to be bent inward rather than outward and thus itis that the thread is completed and sized by this pressure applied tothe end wall of the cap. This submitting of the vertical wall to endwisepressure and the completing of the thread changes the pitch of thethread which is now indicated by the line yy (Fig. 3) and produces thenormal desired pitch of the thread corresponding to the pitch of theholding thread on the neck of the bottle. as one end of the threadterminates adjacent the knurl and the other adjacent the curl, thisendwise pressure necessarily changes slightly the pitch of the threadand this is why the pitch is initially formed slightly greater than thatdesired in the final cap. By this method of forming the completed threadno pressing tool engaging the outer surface of the metal is necessaryother than the threading dies which exert only a light pressure againstthe metal to form the initial shallow thread. Therefore, the surface ofthe metal is undisturbed and unbroken by the forming tools which formand complete the thread.

In Fig. 6, I have shown on an enlarged scale, the preferred shaping ofthe thread which can be accomplished by my improved method. In thisfigure a portion of the bottle neck is indicated at 13. The threadthereon is indicated at 14. The thread on the cap is indicated at 7, 7.The upper depression is where the thread is starting beneath the knurland the lower depression is the completed effective portion of thethread which holds the cap on the bottle.

It will be noted that-the metal between the extreme inner depression inthis figure includes a portion 7 inclined slightly to the vertical and aportion 7 which is inclined slightly to the. horizontal. This provides agripping portion 7 which extends well under the thread 14 0f the bottleneck and holds the cap firmly on the bottle. When the thread is formedby this applied pressure to the vertical wall, the vertical wall takesthe shape shown in detail in Fig. 6. This is due in part to the factthat the metal engages the anvil or horn and when it is limited frommovement further in, then fur- Furthermore,

Inasmuch ther pressure Wlll cause an outward bulging of the wall betweenthe thread depression resulting in this horizontal portion 7 which soeflectlvely engages beneath the thread on the neck of the bottle.

While I have described the cap as being produced from a hat-shaped blankin which shallow threads are formed in the vertical wall by rollingdies, it will be understood that the initial breaking of the metal toform the threads may be formed in other ways. The essential step in thepresent method consists in the subjecting of the blank having theshallow depression to an endwise pressure for the urpose of bending themetal at the formed epression for completing the thread. While I havereferred to the container with which the cap is used as a bottle, itwill be understood that the invention may be applied in the constructionof caps for use on jars or the like and also on metal containers.

Havin fully described my inventionwhat I c aim as new and desire tosecure by Letters Patent is 1. The method of formin caps for bottlesconsisting in orming a hatshaped blank, rolling the vertical wall ofsaid blank to form a shallow thread depression therein, and subjectingsaid vertical wall to endwise pressure for bending the metal in saiddepression to complete the formation of the thread.

2. The method of forming metal screw caps for bottles consisting informing a hatshaped blank, rolling the vertical wall of said blank toform a shallow thread depression therein, the pitch of the thread thusformed being slig tly reater than the desired pitch of the threa on thefinished cap, and subjecting said vertical wall to endwise pressure forbending the metal in said depression to complete the formation of athread of the desired depth and pitch.

3. The method of forming metal screw caps for bottles consisting informing a hatshaped, blank, rolling the vertical wallof said blank toform a shallow thread de ression therein, placin said formed blan on ahorn, subjecting t e vertical wall of said cap to endwise pressure forbending the metal in said depression to complete the formation of thethread, said horn bein so pro ortioned as to limit the inward ben ing oft e metal for producing a thread depression of a redetermined innerdiameter.

In testimony whereof, I aflix my signa\ ture.

WALTER KOWAL.

metal screw

